Variance-based uncertainty relation for incompatible observers

Variance-based uncertainty relation for incompatible observers
Zheng, Xiao; Zhang, Guo-Feng
2017-05-16 00:00:00
Based on mixedness definition as
$$M=1-\hbox {tr}\left( {\rho ^{2}}\right) $$
M
=
1
-
tr
ρ
2
, we obtain a new variance-based uncertainty equality along with an inequality for Hermitian operators of a single-qubit system. The obtained uncertainty equality can be used as a measure of the system mixedness. A qubit system with feedback control is also exploited to demonstrate the new uncertainty.
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